The invention relates generally to apparatus and methods for use in treating proliferative tissue disorders, and more particularly to apparatus and methods for the treatment of such disorders by delivering radiation with a brachytherapy device that also measures treatment characteristics.
Malignant tumors are often treated by surgical resection of the tumor to remove as much of the tumor as possible. Infiltration of the tumor cells into normal tissue surrounding the tumor, however, can limit the therapeutic value of surgical resection because the infiltration can be difficult or impossible to treat surgically. Radiation therapy can be used to supplement surgical resection by targeting the residual malignant cells after resection, with the goal of sterilizing them, reducing the rate of recurrence or delaying the time to recurrence. Radiation therapy can be administered through one of several methods, or a combination of methods, including permanent or temporary interstitial brachytherapy, and external-beam radiation.
Brachytherapy refers to radiation therapy delivered by a spatially confined source of therapeutic rays inserted into the body at or near a tumor or other proliferative tissue disease site. For example, brachytherapy can be performed by implanting radiation sources directly into the tissue to be treated. Brachytherapy is most appropriate where 1) malignant tumor regrowth occurs locally, within 2 or 3 cm of the original boundary of the primary tumor site; 2) radiation therapy is a proven treatment for controlling the growth of the malignant tumor; and 3) there is a radiation dose-response relationship for the malignant tumor, but the dose that can be given safely with conventional external beam radiotherapy is limited by the tolerance or normal tissue. In brachytherapy, radiation doses are highest in close proximity to the radiotherapeutic source, providing a high tumor dose while sparing surrounding normal tissue. Brachytherapy is useful for treating malignant brain and breast tumors, among others.
Prior art brachytherapy devices have provided a number of advancements in the delivery of radiation to target tissue. For example, Winkler U.S. Pat. No. 6,413,204 describes a brachytherapy method and apparatus for treating tissue surrounding a surgically excised tumor with radioactive emissions to kill cancer cells that may be present in the tissue surrounding the excised tumor. The radiation is delivered in a predetermined dose range defined as being between a minimum prescribed absorbed dose for delivering therapeutic effects to tissue that may include cancer cells, and a maximum prescribed absorbed dose above which healthy tissue necrosis may result. The resulting treatment helps to prevent over-exposure to tissue at or near the brachytherapy device, while still delivering the minimum prescribed dose at the maximum prescribed distance from the device.
While such advancements have improved the treatment of proliferative tissue diseases, some challenges remain. Currently, the desired radiation dose is calculated based on the characteristics of the brachytherapy applicator (device), the radiation source and the surrounding tissue, yet the actual dose delivered is not tested to assure that over and/or under treatment do not occur. For example, if the radiation source is a radioactive seed positioned in the center of an expanded balloon, the calculated dose is based on the central positioning of the radiation source. If for some reason the radioactive seed was positioned off center, prior art brachytherapy devices do not have the means to determine that this harmful situation has or is occurring. Prior art brachytherapy devices also lack the ability to directly sense the surrounding tissue and determine the effectiveness of the proliferative tissue disorder treatment.